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    SubjectRe: PROBLEM: conflict between apm and system clock on Inspiron 8100
    Alan Cox wrote:
    > On Mon, 2002-08-26 at 18:00, mike heffner wrote:
    > > Well, isn't that a nice feature. Is there a
    > > workaround for this hardware?
    > A thinkpad ;)

    Unfortunately, that's not true -- I just got an IBM Thinkpad R32
    which exhibits the same behaviour as Mike's Dell Inspiron 8100,
    it's only a tad worse. When I have the battstat_applet running (which
    checks the battery every second), kernel time runs about 3% slow
    compared to the RTC (which seems to be half-way accurate on my machine).

    The cause seems to be definitely APM. If I shut off battstat_applet
    and apmd, kernel time and RTC are in sync. With only apmd, I lose about
    15 seconds per hour. With battstat_applet, I lose 2 minutes per hour.
    while true; do cat /proc/apm >/dev/null; done
    the system runs at about 1/4 of the right speed. Using a kernel with ACPI
    eliminates the problem (of course, you lose almost all power management
    functionality too).

    BTW, I have set CONFIG_APM_ALLOW_INT, and on startup the kernel even says
    "IBM machine detected. Enabling interrupts during APM calls." Doesn't
    seem to help, though.

    Alan Cox continues:
    > In theory you could try writing some code to measure the elapsed time by
    > other means and then correct the kernel for the number of lost ticks.
    > Not trivial. Or for that matter dont run battstat

    I've hacked together a small daemon that tries to adjust the value
    and speed of the kernel clock (via adjtimex) to the RTC. An ugly solution,
    I know, but better than nothing. If anyone is interested, mail me.


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